The invention relates generally to software for a passenger motor vehicle microprocessor and more specifically to software embodying a method for determining when an undersized, oversized, underinflated or overinflated tire or tires are being utilized on a motor vehicle.
Modern space and weight restrictions on passenger motor vehicles have rendered it common for them to be equipped with a mini-spare which has a diameter significantly smaller than the regular or standard vehicle tires. This smaller diameter will cause the tire to rotate at a considerably higher angular velocity or rotational speed than the other, standard, e.g., OEM, tires. Higher angular velocity of a tire can also be caused by a flat tire, an underinflated tire or a tire having, for any reason, a smaller effective or operating diameter. Similarly, an oversized tire or one that is overinflated will rotate more slowly as it exhibits a larger effective diameter.
Depending upon the magnitude of the difference of a particular tire's angular velocity or rotational speed relative to the other tires on a vehicle, performance enhancing systems such as traction control systems and anti-skid systems may exhibit impaired performance. This is because in many systems, front-to-rear or side-to-side wheel (tire) speed differences are the primary control parameters. Hence, an anomaly or offset in the front-to-rear or side-to-side wheel speeds would be interpreted falsely as indicating that the wheels and thus the vehicle are experiencing slip. Depending upon the magnitude of the difference and the sensitivity of the system, this situation may cause false or premature activation of the corrective system and components during driving conditions such as straight line or certain cornering maneuvers which would not normally activate the system.
Accordingly, it is desirable to detect the presence of a mini-spare, a non-standard size tire, an underinflated tire or an overinflated tire so that the performance enhancing system can make appropriate adjustments to reduce or eliminate false or premature system operation.